13 biological factors that make you attracted to someone

Attraction is an unintelligible thing. Sometimes there's no telling what brings you close to one person over another, or what it was that made you realise you can't stop thinking about them.

There are those who are conventionally good looking, but it's actually very subjective whether you fancy someone or not. It can come down to a mixture of biological, psychological, and experience-based factors, and no two people are going to agree on what's attractive and what isn't.

Here are some of the most common reasons people are biologically drawn to each other.

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1. Smell

A study this year found women with certain scents are more attractive to men. It turns out they were most appealing when they had high oestrogen and low progesterone levels. This balance of hormones indicates high female fertility, the researchers explained, so it makes sense that men would find women more attractive while they are at this stage.

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2. Diet

What you eat could also have an impact on how attractive you are. A small study from 2017 found that women were more attracted to sweaty men who ate diets high in produce than men who had more refined carbs like pasta and bread. Essentially, the researchers concluded, when we eat healthy, we might smell healthy too.

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3. Fertility

Being fertile doesn't just make you smell attractive, but it can affect how you look too. One study from a few years ago found that men would rate women's faces and voices as more attractive when their progesterone levels were low and oestrogen levels were high.

5. More hormones

Love is connected with several hormones that make us feel warm and fuzzy. Dopamine is the reward hormone that is released when we do something that makes you feel good, such as spending time with loved ones and having sex. Norepinephrine is also released during attraction, and the combination makes you feel giddy.

Attraction is also associated with higher levels of serotonin, the happy hormone. And physical contact — hugging as well as sexual contact — has been shown to increase oxytocin, the love hormone. So it makes sense that spending more time with someone, enjoying their company, and touching them more would make you feel more attracted to them.

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6. Kindness

If someone is kind, it can make them seem more attractive, and can also make them more likeable. A study showed that putting positive character traits against someone's photo meant people rated them as better looking.

Altruistic behaviour is also attractive, possibly because it was one of the qualities our ancestors favoured in a mate.

"The expansion of the human brain would have greatly increased the cost of raising children, so it would have been important for our ancestors to choose mates both willing and able to be good, long-term parents," Tim Phillips, a psychiatrist at the University of Nottingham, told the Independent. "Displays of altruism could well have provided accurate clues to this, and so led to a link between human altruism and sexual selection."

8. Being similar

Research points to us being attracted to people who are similar to us — both physically and in personality. For example, research from St Andrews showed we are attracted to the features that our parents had when we were born, such as eye colour. This could be because we see them as our first caregiver, and associate positive feelings with their features.

9. Being different

But sometimes, opposites do attract. For instance, if you've lived a sheltered life, you might gravitate towards people who have had extremely different experiences to you.

There may be some biological basis to opposites attracting, too. When it comes to reproduction, a bit of variety works in your favour. For instance, the major histocompatibility complex (MHC) is a part of the immune system that helps cells recognise foreign molecules. When the MHC is vastly different from your mate's, this decreases the danger of mating with someone you're related to, and increases the genetic variability of any offspring you have — meaning they're more likely to be healthier with a better immune system.

10. Maturity

As people mature, they tend to learn more about themselves. This can work in your favour when looking for a partner, because you're more likely to know what you want and what's important to you.

"If you're looking at people when they're younger and dating, they might be attracted to the entire external package and not so concerned with the internal package, meaning somebody's values or their ideas, or the way they treat other people," counselor Michele Kerulis told Elite Daily. "When you start maturing, I think people look more at the overall picture and not just the way somebody looks or that initial sexual attraction."

"Humans don't have strong olfactory skills and kissing allows you to smell and taste a person and see if you have different immune responses as we tend to feel more attracted to someone with a different immune response," Sarah Johns, an expert in human reproduction and evolutionary psychology at the University of Kent, told The Independent.

"The major histocompatibility complex is detectable in body odour, so by kissing and tasting someone it gives the opportunity to assess how similar or different that individual is to you biochemically."

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12. Health

When it comes to heterosexual relationships, several studies have pointed to health being a deciding factor in what people find attractive. It's not necessarily about body shape and size — although low BMI is sometimes a reason, based on distorted social norms.

"In men, attractiveness was predicted positively by masculinity, symmetry, averageness, and negatively by adiposity" — being overweight or obsese — reports one study. "In women, attractiveness was predicted positively by femininity and negatively by adiposity."

Generally, if someone looks healthy — they sleep enough, exercise, and eat well — this will probably show on the outside. And not just in the way they look, but in the way they behave, too.

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13. Facial traits

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There are certain facial characteristics that are proven to be attractive much of the time. Sometimes it's facial symmetry, but other times it's a crooked smile or unique beauty spot that makes someone stand out. Averageness and simple faces are often considered most attractive, possibly because standard faces represent a more diverse set of genes.

On the other hand, familiar faces tend to be most attractive, because people may be influenced more by their personal experiences in life than anything else.

Attraction is an incredibly complicated thing, and science probably won't be able to determine all the reasons you find someone attractive, or vice versa. Often, what's most important is your compatibility, and you're unlikely to be able to quantify that. But there are a few questions you can ask yourself before settling down.